Brahmasutra

The cult of Śiva and the worship of his emblem, the liṅga, are very old. The liṅgas installed in temples are almost always made of stone. They consist of three parts out of which only the third part called as ‘Rudrabhāga’ is seen above the ground. This cylindrical portion alone termed as ‘pujābhāga’ is to be worshiped. It contains certain lines technically called ‘brahmasutra,’ without which the liṅga becomes unfit for worship.